ABSTRACT: In recent years, competition authorities have applied general competition rules in regulated industries, in addition to or instead of the regulation there in force. This raises issues as the two sets of rules are not necessarily identical and the authorities in charge of applying them do not always pursue the same objectives. This article proposes criteria helping to distinguish cases in which competition law is likely to be a more or less useful complement to regulation. As for cases in which competition law may, in principle, be useful, the authors argue for an intervention that accounts for the objectives set by regulation.